If you live anywhere in the northern hemisphere your plumeria is in it's dormancy period. Foliage on the plant during this period should not be an issue in most cases. After leaves fall their condition is defiantly not an issue. The following is an article I wrote several years ago which explanes the phenomena.

Jack

This is a subject that has attached to it, many falsehoods from some very prominent and serious plumeria growers. We have never subscribed to the theory plumeria go dormant to protect themselves from the cold. The following is our reasons:

The fact is the plumeria growerÂs biggest losses are during this period of time in our area/latitude. So if plumeria go dormant as a protection from cold, why are so many trees affected so adversely by the cold?

The answer is very simple: Plumeria in areas of their native habitat go dormant when the day length shortens. Why? Because it is the "DRY" season in this equatorial part of the world. If plumeria did not loose their leaves it would continue transpiration, i.e. loss of water through the leaves leading to total dehydration then imminent death.

Length of day is called "photo period". So when the day length shortens (i.e. photo period) in autumn and winter plumeria go dormant. Because of plumeria genetics and physiology this dormancy is prevalent anywhere in the world a plumeria is exposed to sunlight.

Much study has been done over the past 20 years on various tropical plants, succulents, cacti, true palms and plumeria showing their inability to "harden off" prior to winter as do "woody evergreens, coniferous evergreens and deciduous trees" native to our latitude. My personal experience and association with the Southern California Nursery Industry for over fifty years and growing plumeria for forty years has made this fact very obvious.

The following science is an important fact about tropical plants:

"Plants from tropical and subtropical regions tend to have more saturated fatty acids in their membranes than those from temperate regions (our latitude). Plants which acclimate to low temperatures increase the proportion of unsaturated fatty acids in their membranes."

In Southern California and most latitudes in the US our plumeria become very stressed during this dormancy period. The plant is genetically expecting hot dry conditions but cold and rain is prevalent.

Plumeria cultivated in out of doors conditions should be in the "peak of health" to best survive the conditions of dormancy in our latitude. This becomes the growerÂs responsibility.

Hi Jack.
Great article, thanks for putting it on. .another one to copy and paste..
Karen B

Yes, Jack, that is a great explanation. On the Island of Kauai, I was told that temperature was not believed to be a factor in dormancy. The obvious thinking in that locale, was that the temperature swing there, between summer and winter, was only about 7 degrees, yet, their Plumerias went dormant, just like ours. I suppose my plants suffer less stress during this period, as the South Florida winters remain relatively warm, and it is our dry season... even the humidity is much lower. Thanks for your insights.

Bob

Hi Jack,

I'm trying to understand your statement above. I'm confused about some things you wrote.

1) I've never ever heard the statement that when plumerias go dormant they are safer from cold (until you brought it up!). Who says this? I personally have found my plants are hardiest in the Fall at the end of summer. They can take down to 40s no problem. Over winter I like to keep them warmer, especially in late winter (Feb/March) when they are ready to come out of dormancy.

2) You mention dormancy/leaf discoloration/slowed growth occurs as a result of shortened day length. But you also use the word 'equatorial'. We know that at the equator day lengths are 12 hours, year-round. They neither shorten nor lengthen (right at the equator). So by your logic there can be no dormancy at the equator. And how do plants survive if there's a dry season at the equator if they only go dormant as a result of shorter day lengths?

3) At what point (day length) will a plumeria's growth slow? Is it under 12 hours? Or is it all relative? So if I have a grow light on for 16 hours I can effectively keep them growing year-round, right? If I change the grow light back to 14 hours, will it go into dormancy?

4) I'm not at all understanding your statement:

"Plants which acclimate to low temperatures increase the proportion of unsaturated fatty acids in their membranes."

Because one could ask, well, why don't plumerias simply acclimate and thereby increase their unsaturated fatty acids from prolonged exposures at higher latitudes? Or are you speaking from an 'evolutionary' time-frame vs a growing season time-frame?

I know that you have worked with these plants for many years and we value your experience. But, I just found your statement a bit confusing and contradictory.

Dave,

Think about this; you are not in a locale where plumeria growers leave their trees out year round where this issue is a major topic of discussion. In addition, I don't believe you have that many years of plumeria growing and forum time under your belt as I do. I witness Southern California growers debate this issue every year.

Equatorial photo period does not remain the same year round and this is what causes dormancy. Easily available on the net is a study that confirms my writings. "We know that at the equator day lengths are 12 hours, year-round." The equatorial region as defined by science is a vast environmental space. Your comment "They neither shorten nor lengthen (right at the equator)". Your statement is not accurate according to all all astronomers, experts re. this area. And note this comment "At the equator, day and night always lasts ABOUT the same amount of time (12 hours). ..." note not exact but ABOUT. It is a fact there is a time variable of photo period at the equator. As plumeria studies point out only as much as eighteen minutes in change of daily photo period can make a difference in plumeria dormancy.

I have been in this field for over fifty five years and growing plumeria over forty years and of that forty years a commercial grower of plumeria for ten years.I am also Directer of a Grow More Inc. Fertilizer Research Farm. (this is a very short bio) Also, I have spent thousands of hours of study and research on the science of horticulture and plumeria to bring to the plumeria grower true and accurate information. I invite criticism, questions and whatever however I ask be fair and pursue some research on your own.

I encourage all; to become a knowledgeable plumeria grower TIME MUST be set aside to answer your questions through your own research. You will value your progress more and gain understanding at a more satisfactory rate. Forty years ago there was nothing available to the plumeria grower, now it is simple with Google (etc.) almost anything known to man is available on the internet and in time you will be rewarded with the truthful answers.

Best regards, Jack

Hi Lovefrangis,

I am sorry if I offended you with my reply to Dave. There are many that see plumeria as a hobby as you do and I admire you for having a hobby that is fulfilling to your personal desires. I do the same with fly fishing. However, there are many that admire plumeria with such a passion they become addicted (lol) then desire to know the physiology of the plant, history, detailed growing techniques and so on. Plumeria hobby/collecting is in its infancy as in comparison to the rose as an example.

The craze was started by persons most likely very much like you. As with anything it progresses. As did with my friends Bud Guillot, Curtis Hayes myself and others in the early days here in So Cal. Sadly very little true and accurate horticultural knowledge has been inserted into this phenomenon until present. Now the overwhelming majority have a voracious appetite for details beyond the normal hobbyist. This is definitely where the road is leading us today as did the rosearians in the past.

Dave's questions involve a good deal of advanced plant physiology and detailed knowledge which would take many pages to write. Due to old age and misery, (old saying, lol) I am not physically able to write that prolifically in my present health state. I am sorry for the old man grouchy answers I sometime give when trying to put emphasis on personal research and study.

Lovefrangis,I wish you well in your pursuit of pleasure with your plumeria hobby, Jack

I left town for a few weeks and in the meantime my plumeria (watered by my roommate) has lost most of its leaves. As the leaves drop off, they develop soft brown spots. The tissue feels flaccid. I recently moved the plumeria to another pot hoping it has just outgrown its other one, but it's still losing leaves. The edges of its healthier leaves are black and dry. Could this be some sort of fungus?

I'm no expert, but I think that hkathleenc in CA needs to be aware of some other possible issues besides dormancy. I don't think, without getting more information from the grower, it's possible to diagnosis the problem so easily.

1) Yes, the plant's growth will slow or stop in winter and the leaves will yellow (some can have black areas) before they fall on most plumerias (unless plants are under lights and kept actively growing).

2) Leaf drop and black areas can also result from too strong pesticide/fungicide sprays or drastic changes in environment (temps, etc.)

3) Yellowing and leaf drop can also result from serious mite infestation.

4) There's a chance that it has been overwatered (by roommate?) with resultant root damage. I think it's universally accepted that watering should be reduced during dormancy. Damaged roots can also cause stress to the plant with resultant leaf drop.

5) The stress of repotting (fine root-hair damage) may also cause leaf drop.

6) 'tissues feel flaccid' -- she doesn't say whether this is leaf tissue or stem tissue. When leaves yellow, sometimes they get wilty. I think this is OK. If stem tissue gets soft, then there may be more serious overwatering/rot issues. My dormant plants do not have soft stem tissues. They are turgid, unless they either have rot or unless they have been left too dry for too long.

Just trying to help from my limited growing experiences.

Happy growing!

Dave

For some reason my last post didn't show up.
Jack, no prob! I enjoy reading your posts, they're informative and I'm sure many appreciate your wealth of knowledge. You didn't offend at all, just stated my opinion, for what's it's worth :)
Peace!
L.F.